Following an uneventful installation, I was able to use Planmaker to open a reasonably large spreadsheet prepared in Excel 2010, saved in XLSX, but designed for compatibility with Excel 2003. So far as I have been able to determine, everything is working just fine. Well done.

However, when I attempted to open a similar spreadsheet prepared just for Excel 2007/2010, Planmaker was unable to handle the very useful SUMIFS and COUNTIFS functions (I haven't yet tested for AVERAGEIFS, but assume that is also missing in action). Will these functions be in the final version? If not, I think that your literature should emphasise that Planmaker handles the XLSX format correctly, but is only functionally compatible with Excel 2003 (which, in fairness, is also the case with LibreOffice Calc - but that package is free).

Thanks for the helpful update. I do appreciate that you must be working with a very small development team for the PlanMaker component. SUMIFS, COUNTIFS and AVERAGEIFS would be nice to have, but they are probably not yet deal-breakers. It doesn't really take very long to replace a SUMIFS function with its SUMPRODUCT equivalent (once you have tracked down the absence of a SUMIFS function as the underlying reason for what initially appears to be a completely hosed spreadsheet), and LibreOffice hasn't got around to implementing these functions either.

By contrast, the absence of the promised "bracketed" accounting format for negative sums will continue to be a deal-breaker for many in the English-speaking world. I presume that the European accounting standards use the "-" sign everywhere and, through one of those classic self-fulfilling prophecies, that's where your main market is currently located. The relatively high processing speed of PlanMaker in larger spreadsheets gives it a potential competitive edge over LibreOffice, but you do have to be at least feature-equivalent to persuade customers to pay for your product. Ironically, TextMaker faces a myriad of competitors, but PlanMaker could potentially command a clear majority of the non-Microsoft spreadsheet market were it to be given just a slightly greater share of corporate resources.